Electrodynamic speaker



Jan. 9, 1945. w, HUTTER 2,367,026

ELECTRODYNAMIC SPEAKER Filed Aug. 6, 1941 of the speaker cone.

Patented Jan. 9, 1945 Rock-Ola Manufacturing Corporation,

Chi-

cago, 111., a corporation of Delaware Application August 6, 1941, SerialNo. 405,578

'3 Claims. (01. 179-1155) This invention relates in general to electro-.

dynamicspeakers, and more particularly to improvements for facilitatingtheir use in a vertical position, and for enhancing their tonalqualities.

W'h'en a speaker is placed in a vertical position with the larger oropen end of the cone at the top, the problem of preventing theaccumulasmaller or lower end of'the cone becomes acute. Inan attempt toovercome this difiiculty, a small convex disc has been placed in thelower or smaller end of the cone with its peripheral edge securedthereto, and'a central aperture covered with a thin and porous sheet offelt, or the like, has been provided'in the disc as an air-relief.However, such an arrangement, while preventing access of anythingbutextremely fine particles of'foreign matter to the space or air gapbetween the outer surface of the pole piece and the moving voice coil,merely causes the accumu- -tion of dirt and other foreign matter at thelation of all other foreign matter in the lower end Furthermore, sincethe space between the moving voice coil and the pole piece is only amatter of a few thousandths' of an inch, any particles of foreignmatter, regardless of how small they may be, which are allowed to entersuch space will cause distortion and seriously eifect the operation ofthe speaker.

i 'The'principal object of this invention,therefore, ;is to prevent theaccumulation of any foreign matterin the smaller end of the cone of aspeaker, when the larger end thereof is ripwardly disposed, and toprevent the admittance of any foreign matter to the space or air gapbetween the moving voice coil and the pole piece, by providing means forautomatically removing any foreign matter introduced into the speakercone.

Another important object of the invention is to improve the tonalqualities of a speaker through the use of such foreign mattereliminating means, since the latter increases the area of sound waves ofhigh frequency, and provides superior air relief to prevent damping ofthe low frequencies. A further object of the invention is the pro visionin an electrodynamic speaker of means for automatically draining foreignmatter from the cone thereof, when the larger end of the latterisdisposed upwardly, which comprises a bore extending through the polepiece of the speaker magnet, and a sleeve slidably disposed therein andforming an extension of the smaller endof the cone. i

Numerous other objects and advantages of the invention will beapparentas it is better understood from the following description, which, whentaken in connection with the accompanyingidrawing, discloses a preferredembodiment thereof.

3 In the'drawing, 1

Figure l is a side elevational view of a phonograph or other supportingmember with parts broken away to illustrate the positioning therein of aspeaker embodying the features of the inventiom. I

Fig. 2 is aside-elevation of a preferred form of speaker, with the majorportion thereof shown in section; and v v 1 Fig. 3 is a detailhorizontal section taken sub-' stantially on the line 33 of Fig. 2.

Referring more particularly to the drawing, reference numeral llindicates in general an electrodynamic loud speaker which is mounted ina vertical position, i. e. to transmit sound waves upwardly, at theupper end of a phonograph, resonating column, or other suitablesupporting member 12. The speaker llmay be surrounded by a masking ringl3 for limiting the initial direction of travel of the sound wavestransmitted thereby.

The speaker H comprises *the usual skeleton supporting frame member M tothe lower end of which an lectro-magnet I5 is secured, The magnet I5 issimilar in most respects to those of the prior art, and includes theusual windthe speaker cone which is effective totransmit ing l6 aroundthe central pole piece H. The only difference between the present magnetl5 and those heretofore employed is, that the instant pole piece I1 isprovided with a central bore I8 extending completely therethrough.

The usual voice or moving coil I9 is disposed in the'air gap 2| providedbetween the pole pieces of. the magnet l5. The voice coil I9 is securedin any desirable manner to a ring 22 of 'cardboard, or the like, whichis in turn attached to 1 the usual diaphragm 23. The outer periphery ofthe diaphragm 23 is secured to the electro-magnet l5 by means of theusual clamping rings 24. A sound wave transmitting cone 25 isanchoredat. its outer or larger end to an outer flange of the skeletonsupporting member M by a ring 26. The inner or smaller end of the cone25 extends interiorly of the ring 22 of the voice coil l9, and issecured with the latter to the inner portion of the diaphragm 23., Thesmaller end of the cone 25 terminates in a sleeve portion or flange 21defining a central aperture 28 and extending slidably into the bore 18of the pole piece ll of the electro-magnet l5.

With the above described arrangement, any foreign matter which may findits way into the cone 25 will be permitted to fall freely through theaperture 28 and the bore l8. During operation of the speaker H, thevoice coil I9 will be moved longitudinally of the pole piece H in theusual manner to cause the cone 25 to transmit sound waves correspondingto the varying electrical currents introduced to the speaker. Thisaction of the cone 25 which is attached to the moving coil l 9, willmove any particles of foreign matter deposited therein toward thecentral aperture 28, when the speaker is disposed in the uprightposition of Figs. 1 and 2. Consequently, any foreign matter ,will beautomatically drained from the cone 25, and this action will be; greatlyfacilitated by the flow of air through the bore l8 resulting from theoperation of the cone 25. The sleeve 2? is extended into the bore 18 asufficient distance to prevent the sucking up of any foreign matter intothe space or air gap 21 between the voice coil 19 and the pole pieces ofthe magnet l5. This is of paramount importance, because these spaces arenormally only a few thousandths, of an inch in width, so that anyparticles of foreign matter which might be deposited therein woulddistort the magnetic field and seriously affect the operation of thespeaker.

The above described construction has the additional advantage ofmaterially enhancing the tonal qualities of the speaker. In the firstplace, the central aperture 28 and the bore I8 provide superior airrelief from damping the cone 25 when sound Waves of low frequency arebeing transmitted thereby. In the second place, since the surface of thecone is extended inwardly beyond the ring 22, which is not done in thosespeakers of the prior art having any provision for central air relief,the area at the inner end of the cone which is effective to transmitsound waves of high frequency is materially increased.

It is thought that the invention and many of its attendant advantageswill be understood from the foregoing description, and it will beapparent that various changes may be made in the form, construction andarrangement of the parts Without departing from the spirit and scope ofthe invention or sacrificing all of its material advantages, the formhereinbefore described being merely a preferred embodiment thereof.

I claim:

1. In a speaker having a magnet with a pole piece, a voice coil mountedin spaced relationship to and surrounding an end portion of said polepiece for movement relative thereto, and a cone connected adjacent itssmaller end to said voice coil for movement thereby; means forpreventing the accumulation of foreign matter in said cone to enable useof the speaker in a position in which the larger end of the cone isupwardly disposed, comprising a bore extending through said pole piece,and an aperture at the smaller end of said cone in alignment with saidbore with a depending flange surrounding the same and slidably extendinginto the bore.

2. In a speaker having a magnet with a pole piece, a voice coil mountedin spaced relationship to, and surrounding an end portion of said polepiece, for movement relative thereto, and a cone connected adjacent itssmaller end to said voice coil for movement thereby; means for drainingforeign matter from said cone, when the larger end thereof is disposedupwardly, comprising a bore extending through said pole piece, anaperture in the smaller end of said cone in alignment with said bore,and a sleeve secured to said cone exteriorly of said aperture andslidably extending into said bore a sufficient distance to prevent thesucking up of foreign matter into the space between. said pole piece andsaid voice coil. 3. In a speaker having a magnet with a pole piece, anda voice coil mounted in spaced relationship to and surrounding an endportion of said pole piece for movement relative thereto; means forimproving the tonal qualities of said speaker, comprising a cone havingits smaller end portion secured to said voice coil and extendinginteriorly thereof to increase the area effective to transmit soundwaves of high frequency, a bore extending through said pole piece, andan aperture in said cone in alignment with said bore to provide maximumair relief from damping the sound Waves of low frequency, the smallerend of said cone terminating in a sleeve surrounding said aperture andextending slidably into said bore to automatically drain foreign matterfrom said cone when the speaker is disposed with its larger endextending upwardly, and to prevent the admittance of any foreign matterto the space between said'pole piece and said voice coil.

"WILLIAM H. HUTTER.

